My CH customarily reads around 280, including a test weekend before last. Then this past weekend, armed with my new speedstir, I tested it again. But the sample never turned blue! Instead, around the normal endpoint, it turned CLEAR. Not even a tinge of any color I could discern. Added more drops up to 50, with no additional change.
Thinking that maybe the speedstir was responsible (specifically that I hadn't rinsed the bar sufficiently between tests) I proceeded to retest manually, with the same results - solution turns clear, no blue endpoint at all.
The reagents are about a year old, and have been stored inside, in a dark cool closet. The 0011L is not staining its bottle so seems to still be good. There's never been any indication that I have metals, though I haven't specifically gotten that tested. (The water quality here is sufficiently high that I'd be astounded if there was any notable metal content in the fill water, and I've never used any Cu-containing algaecides or anything. And certainly nothing's changed in that regard since the last normal test.)
Has anybody ever seen this before? Any ideas what's up?